Unlike single function instruments where the firmware is largely static after development, since hardware functionality is predefined and fixed, a multi-purpose test system such as a source measure switching system with plug-in cards that can be removed and inserted in the field does not have this luxury. As new plug-in cards such as switching, signal source, and instrumentation plug-in cards for the platform are developed, inevitably the main firmware of the test system, which can also be referred to as a source measure switching system, will suffer from a lack of awareness and support features for the new plug-in cards that precludes its use without modification.
From a solution standpoint, several options address the issue mentioned above. The simplest option is to mandate firmware upgrades each time a new plug-in card development occurs. While this is the simplest option, it is also the most costly for both the manufacturer and the customer and limits the appeal of the instrument, given the fairly constant need for upgrades to the firmware.
The second option takes classes of general plug-in card descriptors to describe different cards in a reasonably generic manner. Each plug-in card carries a descriptor that the source measure switching system can then read to determine specific properties of the plug-in card. Although this solution offers significantly better adaptability than the first, when a new plug-in card can not fit into one of the existing descriptor classes, a mainframe firmware update would be required in order to describe the functionality of the new class of card. This solution also suffers from the problem that it requires a certain degree of rigidity and conformity, even within a descriptor class, to make the solution viable. This fact effectively limits the ability to create inexpensive hybrid cards that can meet the specific needs of semi-custom, customer-driven applications as an illustrative example.
Test system environments typically require the ability to switch signals from one instrument or instrument to another, be able to measure signals, or detect stimulus actions in a high speed and deterministic manner. Given the space premium found in today's testing environments, test applications require test systems that can provide the ability to detect and generate trigger signals for the test system while occupying the least amount of space and provide for maximum flexibility.